1. Field of the Invention
This invention relates to an electronic level, and specifically to the visual display of such a level suitable for leveling a vertical member such as a fence post or a pole.
2. Description of the Prior Art
Electronic levels such as that sold by Wedge Innovations, Inc. and as disclosed in U.S. Pat. No. 4,912,662 issued Mar. 27, 1990 to Butler, et al., are known in the art. Additional prior art levels are disclosed in U.S. Pat. No. 5,259,188 issued Nov. 9, 1993 to Charles E. Heger using a capacitive level sensing system disclosed in U.S. Pat. No. 5,083,383 to Charles E. Heger, U.S. Pat. No. 5,313,713 issued May 24, 1994 to Charles E. Heger et al., and International (PCT) Patent Application Document No. U.S. Ser. No. 93/07434 having International Publication No. W094/048888 published Mar. 3, 1994 entitled "Electronic Level . . . " invented by Charles E. Heger, et al. These patent disclosures are incorporated herein by reference.
These electronic levels are intended for the typical situation of leveling (or plumbing) a member such as a board during construction. A different type of well known non-electronic level is the fence post or "bullseye" level. This non-electronic "bubble" level has a dome shape for the bubble enclosure. The bubble may move to any position (through 360.degree. and at varying radii) inside the transparent dome, and the bubble position is indicated by a set of cross-hairs and/or concentric circles on the top of the dome. This device is used for "plumbing" a vertical member such as a fence post or a flag pole. In this case, the "leveling" process is done in two dimensions, not just one as for the typical level.
Such bullseye levels are difficult to use, since the direction in which the member (fencepost) must be moved is not intuitively apparent from the bubble position. Thus use of such a device requires a great deal of a trial-and-error due to the need to move the member in two dimensions to achieve the desired null position (verticality, also called plumb).
Further, such prior art devices suffer from the typical drawbacks of non-electronic levels. That is, not readily calibrated by the user; difficult to read in poor light conditions; may not provide the required degree of precision; and provide only a visual, not an audible, indication.
There is a need for an improved fence post level providing a readily understandable display and an indication not only of the vertical (plumb) position but also in which direction(s) the member (fence post) should be moved to achieve the vertical position.